Field of the Invention
The present invention relates to a signal transceiver circuit, and in particular to a signal transceiver circuit capable of processing multi-channel signals.
Description of the Related Art
Presently, mobile devices are highly developed and multi-functional. For example, handheld devices such as mobile phones and tablets are capable of conducting telecommunications, receiving and transmitting e-mails, maintaining social networks, managing contacts, and playing media. Hence, users can implement various applications on their mobile devices, such as a simple phone call, social network interaction, or commercial transaction.
FIG. 1 is a schematic diagram illustrating a conventional prior art signal transceiver circuit. The signal transceiver circuit 100 includes a signal transceiver terminal 102, a choke circuit 104, a band-pass filter 106, a choke circuit 108, a choke circuit 110, a band-pass filter 112, a choke circuit 116, a band-pass filter 118 and a switching device 114, wherein the choke circuit is constituted by inductors and capacitors. The signal transceiver terminal 100 is arranged to receive and transmit a first multi-channel signal SM1 or a second multi-channel signal SM2 from another signal transceiver terminal (figure not shown). It should be noted that the first multi-channel signal SM1 includes a first signal S1 and a second signal S2, and the second multi-channel signal SM2 includes a first signal S1 and a third signal S3, wherein the first signal S1, the second signal S2 and the third signal S3, and the first signal S1, the second signal S2 and the third signal S3 have different frequency bands from each other. The signal transceiver circuit 100 is arranged to split the first signal S1 and the second signal S2 of the first multi-channel signal SM1 and split the first signal S1 and the third signal S3 of second multi-channel signal SM2 by the choke circuit 104, the band-pass filter 106, the choke circuit 108, the choke circuit 110, the band-pass filter 112, the choke circuit 116 and the band-pass filter 118. Moreover, the switching device 114 is selectively coupled to the band-pass filter 106 or the band-pass filter 112 according to the type of the received multi-channel signal for transmitting signals to a specific pin. For example, when the signal transceiver terminal 102 receives the first multi-channel signal SM1, the switching device 114 is coupled to the band-pass filter 112 to transmit and receive the split second signal S2. When the signal transceiver terminal 102 receives the second multi-channel signal SM2, the switching device 114 is coupled to the band-pass filter 106 to transmit and receive the split third signal S3. Moreover, the specific pin can belong to a controller, a signal processor or a signal processing circuit and the specific pin is arranged to transmit and receive the second signal S2 and the third signal S3.
More specifically, the frequency band of the first signal S1 is between the frequency band of the second signal S2 and the frequency band of the third signal S3, and the frequency band of the third signal S3 is higher than the frequency band of the second signal S2, as shown in FIG. 2. The choke circuit 104 is arranged to block signals lower than the frequency band of the second signal S2 and the frequency band of the first signal S1, only the signals having frequencies higher than the frequency band of the third signal S3 are allowed to pass. The band-pass filter 106 only lets signals on the frequency band of the third signal S3 pass. The choke circuit 108 is arranged to block the frequency band of the third signal S3 and signals having frequencies higher than the frequency band of the third signal S3, only the signals on the frequency bands of the first signal S1 and the second signal S2 and signals lower than the frequency band of the first signal S1 and the second signal S2 are allowed to pass. The choke circuit 110 is arranged to block the frequency band of the first signal S1 and signals having frequencies higher than the frequency band of the first signal S1, only the signals on the frequency band of the second signal S2 and the signals lower than the frequency band of the second signal S2 are allowed to pass. The band-pass filter 112 only let signals on the frequency band of the second signal S2 pass. The choke circuit 116 is arranged to block the frequency band of the second signal S2 and signals lower than the frequency band of the second signal S2, only the signals on the frequency band of the first signal S1 and signals higher than the frequency band of the first signal S1 are allowed to pass. The band-pass filter 118 only lets signals on the frequency band of the first signal S1 pass. As described above, the choke circuit 104, the band-pass filter 106, the choke circuit 108, the choke circuit 110, the band-pass filter 112, the choke circuit 116 and the band-pass filter 118 can split the first signal S1 and the second signal S2 from the first multi-channel signal SM1, and split the first signal S1 and the third signal S3 from the second multi-channel signal SM2.
More particularly, the first signal S1 is compatible with a Local Area Network (LAN), such that the frequency band of the first signal S1 is 1125˜1225 MHz. The second signal S2 is compatible with Multimedia over Coax Alliance 1.1 of Wide Area Network (WAN), such that the frequency band of the second signal S2 is 975˜1025 MHz. The third signal S3 is compatible with Multimedia over Coax Alliance 2.0, such that the frequency band of the third signal S3 is 1350˜1675 MHz.
As described above, the signal transceiver circuit 100 can receive and transmit two multi-channel signals SM1/SM2, and split the first signal S2, the second signal S2 and the third signal S3 from the two multi-channel signals SM1/SM2 by four choke circuits 104, 108, 110 and 116 and three band-pass filters 106, 112 and 118.
The cost as well as the entire volume of the signal transceiver circuit 100 depends on the number of the components used. Moreover, because the output terminal is implemented on the end terminal of the switching device 114, where the end terminal can only be coupled to one of the second signal S2 and the third signal S3 at once, the three signals cannot be detected or received at the same time. It should be noted that the signal blocking function of the band-pass filter is achieved by blocking the unwanted signals via short circuit impedance or open circuit impedance. The short circuit impedance or the open circuit impedance can cause the signals with unneeded frequency to flow to the ground through the short circuit or to be blocked by the open circuit, such that signals with unneeded frequency are filtered out. As described above, when the three band-pass filters are arranged in parallel connection without any choke circuit implemented, and when signal rejection of one of the three band-pass filters of the signal transceiver circuit is achieved via short circuit impedance, the signals passing through the other two band-pass filters will be lost or attenuated effected by short circuit impedance. Therefore, the signal rejections of the three band-pass filters is preferable to be achieved via open circuit impedance, such that the signals passing through the other band-pass filters will not be lost or attenuated. In order to reach open circuit impedance, the signal transceiver circuit 100 of FIG. 1 must have choke circuits implemented in front of the band-pass filters 106, 112, 118.
Nevertheless, with the advance of technology, the volume and the component costs of electronic devices are of great importance. Based on a purpose of volume reduction, how to decrease the number of interfaces yet retain a set amount of functions in an electronic device has become a problem that needs to be solved. Aside from this, how to use fewer amount of electronic components to complete the circuit having the same function has become the major problem that the industry must face in order to reduce the volume as well as the overall cost.